RCHeader (Jikes RVM API)

java.lang.Object
- org.mmtk.plan.refcount.RCHeader

```
public class RCHeader
extends Object
```

Field Summary

Fields
Modifier and Type	Field and Description
`static Word`	`BEING_LOGGED`
`static int`	`BITS_USED` Current not using any bits for cycle detection, etc
`static int`	`DEC_ALIVE`
`static int`	`DEC_KILL`
`static Word`	`DOUBLE_INCREMENT`
`static int`	`GC_HEADER_WORDS_REQUIRED`
`static int`	`GLOBAL_GC_BITS_REQUIRED`
`static int`	`INC_NEW`
`static int`	`INC_OLD`
`static Word`	`INCREMENT`
`static int`	`INCREMENT_SHIFT`
`static Word`	`LIVE_THRESHOLD`
`static int`	`LOCAL_GC_BITS_REQUIRED`
`static int`	`LOG_BIT`
`static Word`	`LOGGED`
`static Word`	`LOGGING_MASK`
`static int`	`MARK_BIT` The mark bit used for backup tracing.
`static Word`	`MARK_BIT_MASK`
`static int`	`NEW_BIT` The bit used for newly allocated objects.
`static Word`	`NEW_BIT_MASK`
`static Word`	`READ_MASK`
`static Word`	`refSticky`
`static int`	`refStickyValue`
`static Word`	`UNLOGGED`
`static Word`	`WRITE_MASK`

Constructor Summary

Constructors
Constructor and Description

RCHeader()

Constructors
Constructor and Description
`RCHeader()`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static boolean`	`attemptToLog(ObjectReference object)` Attempt to log `object` for coalescing RC.
`static void`	`clearMarked(ObjectReference object)` Clears the mark status for the given object.
`static int`	`decRC(ObjectReference object)` Decrement the reference count of an object.
`static int`	`getRC(ObjectReference object)` Return the reference count for the object.
`static int`	`incRC(ObjectReference object)` Increment the reference count of an object.
`static void`	`initializeHeader(ObjectReference object, boolean initialInc)` Perform any required initialization of the GC portion of the header.
`static int`	`initRC(ObjectReference object)` Initialize the reference count of an object.
`private static boolean`	`isHeaderMarked(Word header)`
`private static boolean`	`isHeaderNew(Word header)`
`static boolean`	`isLiveRC(ObjectReference object)` Return `true` if given object is live
`static boolean`	`isMarked(ObjectReference object)`
`static boolean`	`isNew(ObjectReference object)`
`private static boolean`	`isStuck(Word value)`
`static boolean`	`logRequired(ObjectReference object)` Return `true` if `object` is yet to be logged (for coalescing RC).
`static void`	`makeLogged(ObjectReference object)` Signify completion of logging `object`.
`static void`	`makeUnlogged(ObjectReference object)` Change `object`'s state to `UNLOGGED`.
`static int`	`remainRC(ObjectReference object)` Retain the reference count of an object.
`static boolean`	`testAndMark(ObjectReference object)` Attempts to atomically mark this object.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - LOCAL_GC_BITS_REQUIRED
```
public static final int LOCAL_GC_BITS_REQUIRED
```
    See Also:
    
    Constant Field Values
  - GLOBAL_GC_BITS_REQUIRED
```
public static final int GLOBAL_GC_BITS_REQUIRED
```
    See Also:
    
    Constant Field Values
  - GC_HEADER_WORDS_REQUIRED
```
public static final int GC_HEADER_WORDS_REQUIRED
```
    See Also:
    
    Constant Field Values
  - LOG_BIT
```
public static final int LOG_BIT
```
    See Also:
    
    Constant Field Values
  - LOGGED
```
public static final Word LOGGED
```
  - UNLOGGED
```
public static final Word UNLOGGED
```
  - BEING_LOGGED
```
public static final Word BEING_LOGGED
```
  - LOGGING_MASK
```
public static final Word LOGGING_MASK
```
  - MARK_BIT
```
public static final int MARK_BIT
```
    The mark bit used for backup tracing.
    
    See Also:
    
    Constant Field Values
  - MARK_BIT_MASK
```
public static final Word MARK_BIT_MASK
```
  - NEW_BIT
```
public static final int NEW_BIT
```
    The bit used for newly allocated objects.
    
    See Also:
    
    Constant Field Values
  - NEW_BIT_MASK
```
public static final Word NEW_BIT_MASK
```
  - BITS_USED
```
public static final int BITS_USED
```
    Current not using any bits for cycle detection, etc
    
    See Also:
    
    Constant Field Values
  - INCREMENT_SHIFT
```
public static final int INCREMENT_SHIFT
```
    See Also:
    
    Constant Field Values
  - INCREMENT
```
public static final Word INCREMENT
```
  - DOUBLE_INCREMENT
```
public static final Word DOUBLE_INCREMENT
```
  - LIVE_THRESHOLD
```
public static final Word LIVE_THRESHOLD
```
  - DEC_KILL
```
public static final int DEC_KILL
```
    See Also:
    
    Constant Field Values
  - DEC_ALIVE
```
public static final int DEC_ALIVE
```
    See Also:
    
    Constant Field Values
  - INC_OLD
```
public static final int INC_OLD
```
    See Also:
    
    Constant Field Values
  - INC_NEW
```
public static final int INC_NEW
```
    See Also:
    
    Constant Field Values
  - refSticky
```
public static final Word refSticky
```
  - refStickyValue
```
public static final int refStickyValue
```
  - WRITE_MASK
```
public static final Word WRITE_MASK
```
  - READ_MASK
```
public static final Word READ_MASK
```
- Constructor Detail
  - RCHeader
```
public RCHeader()
```
- Method Detail
  - logRequired
```
public static boolean logRequired(ObjectReference object)
```
    Return true if object is yet to be logged (for coalescing RC).
    
    Parameters:
    
    object - The object in question
    
    Returns:
    
    true if object needs to be logged.
  - attemptToLog
```
public static boolean attemptToLog(ObjectReference object)
```
    Attempt to log object for coalescing RC. This is used to handle a race to log the object, and returns true if we are to log the object and false if we lost the race to log the object.
    If this method returns true, it leaves the object in the BEING_LOGGED state. It is the responsibility of the caller to change the object to LOGGED once the logging is complete.
    
    Parameters:
    
    object - The object in question
    
    Returns:
    
    true if the race to log objectwas won.
    
    See Also:
    
    makeLogged(ObjectReference)
  - makeLogged
```
public static void makeLogged(ObjectReference object)
```
    Signify completion of logging object. object is left in the LOGGED state.
    
    Parameters:
    
    object - The object whose state is to be changed.
    
    See Also:
    
    attemptToLog(ObjectReference)
  - makeUnlogged
```
public static void makeUnlogged(ObjectReference object)
```
    Change object's state to UNLOGGED.
    
    Parameters:
    
    object - The object whose state is to be changed.
  - isMarked
```
public static boolean isMarked(ObjectReference object)
```
    Parameters:
    
    object - an object
    
    Returns:
    
    whether the object been marked by the most recent backup trace
  - clearMarked
```
public static void clearMarked(ObjectReference object)
```
    Clears the mark status for the given object.
    
    Parameters:
    
    object - the object whose status will be cleared
  - isHeaderMarked
```
private static boolean isHeaderMarked(Word header)
```
    Parameters:
    
    header - the header
    
    Returns:
    
    whether the header has been marked
  - testAndMark
```
public static boolean testAndMark(ObjectReference object)
```
    Attempts to atomically mark this object.
    
    Parameters:
    
    object - the object to mark
    
    Returns:
    
    true if the mark was performed, false otherwise
  - isNew
```
public static boolean isNew(ObjectReference object)
```
    Parameters:
    
    object - an object
    
    Returns:
    
    whether the object has been marked as new
  - isHeaderNew
```
private static boolean isHeaderNew(Word header)
```
    Parameters:
    
    header - an object's header
    
    Returns:
    
    whether the header has a new marking
  - initializeHeader
```
public static void initializeHeader(ObjectReference object,
                                    boolean initialInc)
```
    Perform any required initialization of the GC portion of the header.
    
    Parameters:
    
    object - the object
    
    initialInc - start with a reference count of 1 (0 if false)
  - isLiveRC
```
public static boolean isLiveRC(ObjectReference object)
```
    Return true if given object is live
    
    Parameters:
    
    object - The object whose liveness is to be tested
    
    Returns:
    
    true if the object is alive
  - getRC
```
public static int getRC(ObjectReference object)
```
    Return the reference count for the object.
    
    Parameters:
    
    object - The object whose liveness is to be tested
    
    Returns:
    
    true if the object is alive
  - incRC
```
public static int incRC(ObjectReference object)
```
    Increment the reference count of an object. Return either INC_OLD if the object is not new, INC_NEW if the object is new.
    
    Parameters:
    
    object - The object whose RC is to be incremented.
    
    Returns:
    
    INC_OLD if the object is not new, INC_NEW if the object is new.
  - decRC
```
public static int decRC(ObjectReference object)
```
    Decrement the reference count of an object. Return either DEC_KILL if the count went to zero, DEC_ALIVE if the count did not go to zero.
    
    Parameters:
    
    object - The object whose RC is to be decremented.
    
    Returns:
    
    DEC_KILL if the count went to zero, DEC_ALIVE if the count did not go to zero.
  - initRC
```
public static int initRC(ObjectReference object)
```
    Initialize the reference count of an object. Return either INC_OLD if the object is not new, INC_NEW if the object is new.
    
    Parameters:
    
    object - The object whose RC is to be initialized.
    
    Returns:
    
    INC_OLD if the object is not new, INC_NEW if the object is new.
  - remainRC
```
public static int remainRC(ObjectReference object)
```
    Retain the reference count of an object. Return either INC_OLD if the object is not new, INC_NEW if the object is new.
    
    Parameters:
    
    object - The object whose RC is to be retained.
    
    Returns:
    
    INC_OLD if the object is not new, INC_NEW if the object is new.
  - isStuck
```
private static boolean isStuck(Word value)
```
    Parameters:
    
    value - a word
    
    Returns:
    
    whether the word contains a sticky marking

Class RCHeader

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOCAL_GC_BITS_REQUIRED

GLOBAL_GC_BITS_REQUIRED

GC_HEADER_WORDS_REQUIRED

LOG_BIT

LOGGED

UNLOGGED

BEING_LOGGED

LOGGING_MASK

MARK_BIT

MARK_BIT_MASK

NEW_BIT

NEW_BIT_MASK

BITS_USED

INCREMENT_SHIFT

INCREMENT

DOUBLE_INCREMENT

LIVE_THRESHOLD

DEC_KILL

DEC_ALIVE

INC_OLD

INC_NEW

refSticky

refStickyValue

WRITE_MASK

READ_MASK

Constructor Detail

RCHeader

Method Detail

logRequired

attemptToLog

makeLogged

makeUnlogged

isMarked

clearMarked

isHeaderMarked

testAndMark

isNew

isHeaderNew

initializeHeader

isLiveRC

getRC

incRC

decRC

initRC

remainRC

isStuck